The present invention relates to electrochemical batteries.
Many types of Chemoelectric batteries such as fuel cell batteries, metal air batteries, and advanced versions of established batteries like the alkaline accumulator, the lead acid battery, etc., are frequently built in the form of a pile or in so-called filterpress configuration. Such a pile is frequently built of elements with a preferably planar form which are stacked and joined to each other so as to produce a continuous pile. The pile contains electrodes electrolyte spaces and channels for the supply of electrolyte, coolant, reactants, etc. Individual cells are formed in this way within the pile, which cells contain a functional positive electrode, an electrolyte space and a functional negative electrode. Such cells may be coupled in parallel in groups, which groups in turn are coupled in series. There are also, of course, other embodiments with cells only coupled in series where the positive electrode in one cell is electrically coupled to the negative electrode in the adjacent cell, etc. More complicated patterns are possible which are determined by the desire to reduce leakage currents in the electrolyte system and to create conditions for special electrical control modes with in-and-out coupling of individual parts of the pile.
Battery designs of this kind are well-known in the state of art and are described for instance in Swedish Pat. No. 217,054.
A battery pile is frequently made up of elements which operate independently of each other (exclusive of the necessary means for electrical and mechanical couplings). It is, however, frequently advantageous to join together the different electrolyte spaces which are formed in the pile so as to produce a common electrolyte system. A common design which is described for instance in the above-named Swedish Pat. No. 217,054 uses one electrolyte channel for incoming electrolyte, which channel is connected to the different electrolyte spaces by means of so-called bi-channels. There is also a channel for outgoing electrolyte to which the different electrolyte spaces are connected in a similar way be means of bi-channels. Electrolyte can be circulated through the different electrolyte spaces in this way from a common separate electrolyte system. This produces a number of advantages, such as for instance, the possibility of temperature control, elimination of concentration differences, purification, etc.
A special embodiment of this kind with a common electrolyte system is described in Swedish Pat. No. 363,193 and is characterized in that the electrolyte is allowed to flow freely out of the pile over a free board instead of by means of a system with bi-channels and a main channel. This embodiment gives great advantages among other things in conjunction with iron air batteries built in pile shape, since the oxygen which is developed during charge can escape freely from the pile.
The present invention is thus concerned with electrochemical power sources which are in principal built as piles and which contain a common electrolyte system for the cells in the pile, whereby the electrical design of the pile is such that the pile contains at least two units or modules which are electrically coupled in series and which units or modules contain at least two cells coupled in parallel. The invention is a remedy to a difficult problem with previously known batteries which have a common electrolyte system for the cells in the battery. The electrolyte system in such previous batteries would connect cell spaces of different potentials which would cause leakage currents in the electrolyte channels. The natural way to reduce leakage currents is to minimize the dimensions of the electrolyte channels. This, however, increases the risk for plugging of the channels with sludge, etc. Therefore one is, in practice, forced to make a compromise between the desire for good electrolyte connections and high resistance in these connections.
The supply of electrolyte to an individual cell space may be cut off by a sludge formation which will shut off, for instance, a bi-channel for the incoming electrolyte even when these channels are comparatively large. Such incidents frequently cause secondary effects. These disturbances can be enhanced for instance because of temperature rises in the cell space in question, because of insufficient cooling which will in turn increase the sludge formation. This in turn can then lead to a situation wherein the electrolyte space looses electrolyte so that a gas space is formed in the electrolyte space. Because of this, electrodes which are still in contact with electrolyte will then take a very strong current load. There is also a risk of formation of incrusts at the interface between the gas phase and the electrolyte phase. These cooperating effects cause failure in one individual cell, whereas other cells are completely intact. This may seem unbelievable with piles which have been built with small tolerances and where the electrodes are of uniform size and quality.
It is therefore an object to provide a novel electrochemical battery which alleviates problems of the type previously described.
It is another object of the invention to provide a novel electrochemical battery which enables cells to be fluidly connected while minimizing potential electrical leakage.